Objective: Recommendations for the treatment of cytokine release syndrome/macrophage activation syndrome (MAS) associated with coronavirus disease-2019 (COVID-19) are still of poor quality. IL-6 is an important therapeutic target as a main mediator of cytokine storm. The aim of our study was to evaluate the tocilizumab (TCZ) efficacy and factors affecting the therapy outcome. Methods: This retrospective study included 27 patients treated with TCZ for COVID-19-MAS. All patients in this study were treated with TCZ (intravenously, at a dose of 8 mg kg 1) in addition to standard therapy. Clinical improvement (survival and decreased oxygen demand) on the 10-14th days and secondary infection rate were assessed. Results: In our 27 treated patients, 14 (51.8%) received TCZ in the intensive care unit (ICU) and seven (25.9%) were need to invasive mechanical ventilation (IMV). Fifteen (55.6%) of these patients revealed a good clinical response (four patients discharge from the ICU and 11 patients who followed-up in non- ICU beds showed a decrease in oxygen demand). TCZ was significantly less effective in patients having high Murray lung injury score, low PO2/FiO2 ratio, IMV, and ICU admission (P < .05). Severity of hypoxemia was found as a single independent risk factor in the multivariable analysis (P < .05). Secondary bacterial infections rate was significantly higher in intubated patients (P < .01) or treated in the ICU (P ¼ .01). Conclusion: TCZ was showed limited efficacy for COVID-19-related MAS. The most important predictive indicator for therapy outcome was found as the severity of hypoxemia. In addition, IMV and/or ICU was associated with the poor outcome and high side effect. So, controlled trials are still needed to confirm the indications and timing of TCZ therapy.